All classes that implement SolrBackendInterface in Search API Solr 4.x
- class \Drupal\search_api_solr\Plugin\search_api\backend\SearchApiSolrBackend extends \Drupal\search_api\Backend\BackendPluginBase implements PluginFormInterface, SolrAutocompleteInterface, SolrBackendInterface uses \Drupal\search_api\Plugin\PluginFormTrait, DependencySerializationTrait, PluginDependencyTrait, SolrCommitTrait